A high voltage transmission line has an aluminum cable of diameter 3.0 cm , 200 km long . What is the resistance of this cable?

Harleen asked

**Answer**:

Use the relation R = ρ l/A

A= πr^{2} =πd^{2}/4

= 3.14 x 3 x 10^{-2}x 3 x 10^{-2}/4

ρ= 2.82×10^{−8 }ohm m

l = 200km = 200000 m = 2 x 10^{5}m

*You can now just substitute the values and get the answer.*